Selective tungsten removal

ABSTRACT

Exemplary methods for removing tungsten-containing material may include flowing a chlorine-containing precursor into a processing region of a semiconductor processing chamber. The methods may also include flowing methane into the processing region of the semiconductor processing chamber. The methods may include forming a plasma from the chlorine-containing precursor and the methane to produce plasma effluents. The methods may also include contacting a substrate with the plasma effluents. The substrate may include an exposed region of a tungsten-containing material. The plasma effluents may produce an oxychloride of tungsten. The methods may also include recessing the exposed region of the tungsten-containing material.

TECHNICAL FIELD

The present technology relates to semiconductor processes and equipment. More specifically, the present technology relates to etching tungsten-containing materials.

BACKGROUND

Integrated circuits are made possible by processes which produce intricately patterned material layers on substrate surfaces. Producing patterned material on a substrate requires controlled methods for removal of exposed material. Chemical etching is used for a variety of purposes including transferring a pattern in photoresist into underlying layers, thinning layers, or thinning lateral dimensions of features already present on the surface. Often it is desirable to have an etch process that etches one material faster than another facilitating, for example, a pattern transfer process. Such an etch process is said to be selective to the first material. As a result of the diversity of materials, circuits, and processes, etch processes have been developed with a selectivity towards a variety of materials.

Etch processes may be termed wet or dry based on the materials used in the process. A wet HF etch preferentially removes silicon oxide over other dielectrics and materials. However, wet processes may have difficulty penetrating some constrained trenches and also may sometimes deform the remaining material. Dry etches produced in local plasmas formed within the substrate processing region can penetrate more constrained trenches and exhibit less deformation of delicate remaining structures. However, local plasmas may damage the substrate through the production of electric arcs as they discharge.

Thus, there is a need for improved systems and methods that can be used to produce high quality devices and structures. These and other needs are addressed by the present technology.

SUMMARY

Exemplary methods for etching one or more tungsten-containing materials may include flowing a chlorine-containing precursor into a processing region of a semiconductor processing chamber. The etching methods may also include flowing methane into the processing region of the semiconductor processing chamber. The etching methods may include forming a plasma from the chlorine-containing precursor and the methane to produce plasma effluents. The etching methods may further include contacting a substrate with the plasma effluents. The substrate may include an exposed region of a tungsten-containing material. The plasma effluents may produce an oxychloride of tungsten. The etching methods may also include recessing the exposed region of the tungsten-containing material.

In exemplary methods, the tungsten-containing material may include at least one of tungsten oxide or tungsten metal. In some embodiments, the etching methods may remove the tungsten-containing material at a rate of at least about 200 Å per minute. In some embodiments, the etching methods may remove the tungsten-containing material at a rate of at least about 400 Å per minute. The substrate may further include an exposed region of a silicon-containing material. The etching methods may have a selectivity of the tungsten-containing material to the silicon-containing material greater than or about 100:1. The silicon-containing material may define a trench within which at least a portion of the tungsten-containing material may be disposed. The trench may have an aspect ratio of about 10:1 or greater. The etching methods may completely remove at least the portion of the tungsten-containing material disposed within the trench. A temperature of the substrate may be maintained between about 200° C. and about 400° C. during the etching method. The temperature of the substrate may be maintained at about 250° C. during the etching method. A plasma power of the plasma formed from the chlorine-containing precursor and the methane may be at least about 5 W. The plasma power of the plasma formed from the chlorine-containing precursor and the methane may be less than or about 250 W. A pressure within the semiconductor processing chamber may be maintained below or about 3 Torr. In some embodiments, the etching methods may be repeated for at least two cycles. Each of the at least two cycles may last less than or about 30 seconds. A flow rate of the methane may be below or about 30 sccm. The chlorine-containing precursor may include diatomic chlorine. The flow rate of the diatomic chlorine may be about 120 sccm.

The present technology may also include additional exemplary methods of etching one or more tungsten-containing materials. The etching methods may include flowing a chlorine-containing precursor into a processing region of a semiconductor processing chamber. The etching methods may also include flowing a hydrocarbon precursor into the processing region of the semiconductor processing chamber. The etching methods may include forming a plasma from the chlorine-containing precursor and the hydrocarbon precursor to produce plasma effluents. The etching methods may further include contacting a substrate with the plasma effluents. The substrate may include a first region of a tungsten-containing material and a second region of a first silicon-containing material. The etching methods may include selectively etching the first region of the tungsten-containing material relative to the second region of the first silicon-containing material.

In exemplary methods, the plasma effluents may produce an oxychloride of tungsten. The substrate may further include a metal nitride liner interposed between a third region of the tungsten-containing material and a fourth region of a second silicon-containing material. The etching methods may further include selectively etching the metal nitride liner relative to the first and the second silicon-containing material.

The present technology may also include additional exemplary methods of etching one or more tungsten-containing materials. The etching methods may include flowing diatomic chlorine at less than or about 250 sccm into a processing region of a semiconductor processing chamber. The etching method may also include flowing methane at less than or about 50 sccm into the processing region of the semiconductor processing chamber. The etching method may include forming a plasma from the diatomic chlorine and the methane at a plasma power of between about 10 W and about 250 W to produce plasma effluents. The etching methods may further include contacting a substrate with the plasma effluents. The substrate may include an exposed region of a tungsten-containing material and an exposed region of a silicon-containing material. The etching method may include etching the exposed region of the tungsten-containing material at a rate of at least about 400 Å per minute. The etching method may have a selectivity of the tungsten-containing material to the silicon-containing material greater than 100:1. In some embodiments, a temperature of the substrate may be maintained at about 250° C. during the etching of the exposed region of the tungsten-containing material. In some embodiments, a pressure of the semiconductor processing chamber may be maintained at or below about 10 Torr during the etching of the exposed region of the tungsten-containing material.

Such technology may provide numerous benefits over conventional systems and techniques. For example, the etching methods may remove tungsten-containing materials at relatively low temperatures with a high etch rate of the tungsten-containing materials and a high selectivity of the tungsten-containing materials to inter-layer dielectric materials. The etching methods may be controlled to remove tungsten-containing materials from a trench of very high aspect ratios and leave minimal or no residue inside the trench. These and other embodiments, along with many of their advantages and features, are described in more detail in conjunction with the below description and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the disclosed technology may be realized by reference to the remaining portions of the specification and the drawings.

FIG. 1 shows a top plan view of one embodiment of an exemplary processing system according to embodiments of the present technology.

FIG. 2A shows a schematic cross-sectional view of an exemplary processing chamber according to embodiments of the present technology.

FIG. 2B shows a detailed view of a portion of the processing chamber illustrated in FIG. 2A according to embodiments of the present technology.

FIG. 3 shows a bottom plan view of an exemplary showerhead according to embodiments of the present technology.

FIG. 4 shows exemplary operations in a method according to embodiments of the present technology.

FIGS. 5A-5C show cross-sectional views of substrates being processed according to embodiments of the present technology.

Several of the figures are included as schematics. It is to be understood that the figures are for illustrative purposes, and are not to be considered of scale unless specifically stated to be of scale. Additionally, as schematics, the figures are provided to aid comprehension and may not include all aspects or information compared to realistic representations, and may include exaggerated material for illustrative purposes.

In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a letter that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the letter.

DETAILED DESCRIPTION

As semiconductor device features continue to reduce in size, so do the interconnects between the features. The use of tungsten oxide can be advantageous in advanced patterning. However, etching tungsten oxide poses several challenges. For example, the etch rate for tungsten oxide with NF₃ is very low, which leads to long processing times. Additionally, high temperatures are generally required for removing tungsten oxide, which may result in removal of inter-layer dielectric materials, causing damages to features formed on a substrate. Moreover, long processing time coupled with high processing temperature used for tungsten-based removal may exceed thermal budgets during mid-line and back-end-of-line processing. Furthermore, given the high aspect ratios of vias and trenches, complete removal of tungsten-containing materials disposed inside a via or trench can be difficult. Any residual material left inside the via or trench after an etching operation may cause peeling of subsequently formed or deposited materials and may affect properties of the materials and the semiconductor device.

The present technology overcomes these issues by providing an etching method that removes tungsten oxide and optionally also removes tungsten metal inside a via or trench. The etching method preserves features formed on the substrate by etching tungsten oxide and/or tungsten metal at low temperatures with a high etch rate and a high selectivity of the tungsten-containing materials over inter-layer dielectric materials. The etching method may be controlled for complete removal of tungsten oxide and/or tungsten metal and leave little or no residue inside the via or trench. Additionally, because the etching method operates at temperatures significantly lower than conventional etching techniques while still offering high etch rates, the present technology can be applied to semiconductor devices characterized by a lower thermal budget.

Although the remaining disclosure will routinely identify specific etching processes utilizing the disclosed technology, it will be readily understood that the systems and methods are equally applicable to deposition and cleaning processes as may occur in the described chambers. Accordingly, the technology should not be considered to be so limited as for use with etching processes or chambers alone. Moreover, although an exemplary chamber is described to provide foundation for the present technology, it is to be understood that the present technology can be applied to virtually any semiconductor processing chamber that may allow the single-chamber operations described.

FIG. 1 shows a top plan view of one embodiment of a processing system 100 of deposition, etching, baking, and curing chambers according to embodiments. In the figure, a pair of front opening unified pods (FOUPs) 102 supply substrates of a variety of sizes that are received by robotic arms 104 and placed into a low pressure holding area 106 before being placed into one of the substrate processing chambers 108 a-f, positioned in tandem sections 109 a-c. A second robotic arm 110 may be used to transport the substrate wafers from the holding area 106 to the substrate processing chambers 108 a-f and back. Each substrate processing chamber 108 a-f, can be outfitted to perform a number of substrate processing operations including the dry etch processes described herein in addition to cyclical layer deposition (CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), etch, pre-clean, degas, orientation, and other substrate processes.

The substrate processing chambers 108 a-f may include one or more system components for depositing, annealing, curing and/or etching a dielectric or metallic film on the substrate wafer. In one configuration, two pairs of the processing chambers, e.g., 108 c-d and 108 e-f, may be used to deposit material on the substrate, and the third pair of processing chambers, e.g., 108 a-b, may be used to etch the deposited material. In another configuration, all three pairs of chambers, e.g., 108 a-f, may be configured to etch a dielectric or metallic film on the substrate. Any one or more of the processes described may be carried out in chamber(s) separated from the fabrication system shown in different embodiments. It will be appreciated that additional configurations of deposition, etching, annealing, and curing chambers for dielectric films are contemplated by system 100.

FIG. 2A shows a cross-sectional view of an exemplary process chamber system 200 with partitioned plasma generation regions within the processing chamber. During film etching, e.g., titanium nitride, tantalum nitride, tungsten, copper, cobalt, silicon, polysilicon, silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbide, etc., a process gas may be flowed into the first plasma region 215 through a gas inlet assembly 205. A remote plasma system (RPS) 201 may optionally be included in the system, and may process a first gas which then travels through gas inlet assembly 205. The inlet assembly 205 may include two or more distinct gas supply channels where the second channel (not shown) may bypass the RPS 201, if included.

A cooling plate 203, faceplate 217, ion suppressor 223, showerhead 225, and a substrate support 265, having a substrate 255 disposed thereon, are shown and may each be included according to embodiments. The pedestal 265 may have a heat exchange channel through which a heat exchange fluid flows to control the temperature of the substrate, which may be operated to heat and/or cool the substrate or wafer during processing operations. The wafer support platter of the pedestal 265, which may comprise aluminum, ceramic, or a combination thereof, may also be resistively heated in order to achieve relatively high temperatures, such as from up to or about 100° C. to above or about 600° C., using an embedded resistive heater element.

The faceplate 217 may be pyramidal, conical, or of another similar structure with a narrow top portion expanding to a wide bottom portion. The faceplate 217 may additionally be flat as shown and include a plurality of through-channels used to distribute process gases. Plasma generating gases and/or plasma excited species, depending on use of the RPS 201, may pass through a plurality of holes, shown in FIG. 2B, in faceplate 217 for a more uniform delivery into the first plasma region 215.

Exemplary configurations may include having the gas inlet assembly 205 open into a gas supply region 258 partitioned from the first plasma region 215 by faceplate 217 so that the gases/species flow through the holes in the faceplate 217 into the first plasma region 215. Structural and operational features may be selected to prevent significant backflow of plasma from the first plasma region 215 back into the supply region 258, gas inlet assembly 205, and fluid supply system 210. The faceplate 217, or a conductive top portion of the chamber, and showerhead 225 are shown with an insulating ring 220 located between the features, which allows an AC potential to be applied to the faceplate 217 relative to showerhead 225 and/or ion suppressor 223. The insulating ring 220 may be positioned between the faceplate 217 and the showerhead 225 and/or ion suppressor 223 enabling a capacitively coupled plasma (CCP) to be formed in the first plasma region. A baffle (not shown) may additionally be located in the first plasma region 215, or otherwise coupled with gas inlet assembly 205, to affect the flow of fluid into the region through gas inlet assembly 205.

The ion suppressor 223 may comprise a plate or other geometry that defines a plurality of apertures throughout the structure that are configured to suppress the migration of ionically-charged species out of the first plasma region 215 while allowing uncharged neutral or radical species to pass through the ion suppressor 223 into an activated gas delivery region between the suppressor and the showerhead. In embodiments, the ion suppressor 223 may comprise a perforated plate with a variety of aperture configurations. These uncharged species may include highly reactive species that are transported with less reactive carrier gas through the apertures. As noted above, the migration of ionic species through the holes may be reduced, and in some instances completely suppressed. Controlling the amount of ionic species passing through the ion suppressor 223 may advantageously provide increased control over the gas mixture brought into contact with the underlying wafer substrate, which in turn may increase control of the deposition and/or etch characteristics of the gas mixture. For example, adjustments in the ion concentration of the gas mixture can significantly alter its etch selectivity, e.g., SiNx:SiOx etch ratios, Si:SiOx etch ratios, etc. In alternative embodiments in which deposition is performed, it can also shift the balance of conformal-to-flowable style depositions for dielectric materials.

The plurality of apertures in the ion suppressor 223 may be configured to control the passage of the activated gas, i.e., the ionic, radical, and/or neutral species, through the ion suppressor 223. For example, the aspect ratio of the holes, or the hole diameter to length, and/or the geometry of the holes may be controlled so that the flow of ionically-charged species in the activated gas passing through the ion suppressor 223 is reduced. The holes in the ion suppressor 223 may include a tapered portion that faces the plasma excitation region 215, and a cylindrical portion that faces the showerhead 225. The cylindrical portion may be shaped and dimensioned to control the flow of ionic species passing to the showerhead 225. An adjustable electrical bias may also be applied to the ion suppressor 223 as an additional means to control the flow of ionic species through the suppressor.

The ion suppressor 223 may function to reduce or eliminate the amount of ionically charged species traveling from the plasma generation region to the substrate. Uncharged neutral and radical species may still pass through the openings in the ion suppressor to react with the substrate. It should be noted that the complete elimination of ionically charged species in the reaction region surrounding the substrate may not be performed in embodiments. In certain instances, ionic species are intended to reach the substrate in order to perform the etch and/or deposition process. In these instances, the ion suppressor may help to control the concentration of ionic species in the reaction region at a level that assists the process.

Showerhead 225 in combination with ion suppressor 223 may allow a plasma present in first plasma region 215 to avoid directly exciting gases in substrate processing region 233, while still allowing excited species to travel from chamber plasma region 215 into substrate processing region 233. In this way, the chamber may be configured to prevent the plasma from contacting a substrate 255 being etched. This may advantageously protect a variety of intricate structures and films patterned on the substrate, which may be damaged, dislocated, or otherwise warped if directly contacted by a generated plasma. Additionally, when plasma is allowed to contact the substrate or approach the substrate level, the rate at which oxide species etch may increase. Accordingly, if an exposed region of material is oxide, this material may be further protected by maintaining the plasma remotely from the substrate.

The processing system may further include a power supply 240 electrically coupled with the processing chamber to provide electric power to the faceplate 217, ion suppressor 223, showerhead 225, and/or pedestal 265 to generate a plasma in the first plasma region 215 or processing region 233. The power supply may be configured to deliver an adjustable amount of power to the chamber depending on the process performed. Such a configuration may allow for a tunable plasma to be used in the processes being performed. Unlike a remote plasma unit, which is often presented with on or off functionality, a tunable plasma may be configured to deliver a specific amount of power to the plasma region 215. This in turn may allow development of particular plasma characteristics such that precursors may be dissociated in specific ways to enhance the etching profiles produced by these precursors.

A plasma may be ignited either in chamber plasma region 215 above showerhead 225 or substrate processing region 233 below showerhead 225. Plasma may be present in chamber plasma region 215 to produce the radical precursors from an inflow of, for example, a fluorine-containing precursor or other precursor. An AC voltage typically in the radio frequency (RF) range may be applied between the conductive top portion of the processing chamber, such as faceplate 217, and showerhead 225 and/or ion suppressor 223 to ignite a plasma in chamber plasma region 215 during deposition. An RF power supply may generate a high RF frequency of 13.56 MHz but may also generate other frequencies alone or in combination with the 13.56 MHz frequency.

FIG. 2B shows a detailed view 253 of the features affecting the processing gas distribution through faceplate 217. As shown in FIGS. 2A and 2B, faceplate 217, cooling plate 203, and gas inlet assembly 205 intersect to define a gas supply region 258 into which process gases may be delivered from gas inlet 205. The gases may fill the gas supply region 258 and flow to first plasma region 215 through apertures 259 in faceplate 217. The apertures 259 may be configured to direct flow in a substantially unidirectional manner such that process gases may flow into processing region 233, but may be partially or fully prevented from backflow into the gas supply region 258 after traversing the faceplate 217.

The gas distribution assemblies such as showerhead 225 for use in the processing chamber section 200 may be referred to as dual channel showerheads (DCSH) and are additionally detailed in the embodiments described in FIG. 3. The dual channel showerhead may provide for etching processes that allow for separation of etchants outside of the processing region 233 to provide limited interaction with chamber components and each other prior to being delivered into the processing region.

The showerhead 225 may comprise an upper plate 214 and a lower plate 216. The plates may be coupled with one another to define a volume 218 between the plates. The coupling of the plates may be so as to provide first fluid channels 219 through the upper and lower plates, and second fluid channels 221 through the lower plate 216. The formed channels may be configured to provide fluid access from the volume 218 through the lower plate 216 via second fluid channels 221 alone, and the first fluid channels 219 may be fluidly isolated from the volume 218 between the plates and the second fluid channels 221. The volume 218 may be fluidly accessible through a side of the gas distribution assembly 225.

FIG. 3 is a bottom view of a showerhead 325 for use with a processing chamber according to embodiments. Showerhead 325 may correspond with the showerhead 225 shown in FIG. 2A. Through-holes 365, which show a view of first fluid channels 219, may have a plurality of shapes and configurations in order to control and affect the flow of precursors through the showerhead 225. Small holes 375, which show a view of second fluid channels 221, may be distributed substantially evenly over the surface of the showerhead, even amongst the through-holes 365, and may help to provide more even mixing of the precursors as they exit the showerhead than other configurations.

The chambers discussed previously may be used in performing exemplary methods including etching methods. Turning to FIG. 4, exemplary operations of a method 400 according to embodiments of the present technology are shown. Prior to the first operation of the method, a substrate may be processed in one or more ways before being placed within a processing region of a chamber in which method 400 may be performed. For example, features may be produced, and vias or trenches may be formed or defined within the substrate. The vias or trenches may have an aspect ratio, or a ratio of their height to width, greater than or about 2, greater than or about 5, greater than or about 10, greater than or about 20, greater than or about 30, greater than or about 50, or more in embodiments. The vias or trenches may be formed through or within one or more layers of inter-layer dielectric materials, such as silicon oxide and/or silicon nitride. Thus, the sidewalls of the via or trench may be defined by one or more inter-layer dielectric materials in embodiments. Additionally, a liner material may be formed along the trench sidewalls to protect the substrate from metal diffusion.

Furthermore, one or more tungsten-containing materials may be deposited within a trench. For example, tungsten metal may be deposited within a processing chamber positioned on a processing tool. The chamber in which deposition is performed may be on the same tool as an etching chamber used in method 400, or in embodiments may be on a tool different from the chamber used in method 400. A portion or all of the tungsten metal may be oxidized to form tungsten oxide within the same or a different processing chamber in which deposition is performed. Accordingly, a pillar of tungsten metal, a pillar of tungsten oxide, or a pillar of a combination of tungsten oxide and tungsten metal may be formed within the trench in embodiments. The substrate may then be transferred to a chamber, such as chamber 200 described above, for method 400 to be performed.

Method 400 may include flowing one or more precursors into a processing region of a semiconductor processing chamber at operation 405. The processing region may be region 233 of chamber 200 previously discussed, where the substrate including one or more tungsten-containing materials may be housed. In some embodiments, the one or more precursors may include one or more halogen-containing precursors. In some embodiments, the one or more precursors may further include one or more hydrocarbon precursors. A plasma may be formed at operation 410 within the processing region of the chamber. The plasma may be formed from the one or more halogen-containing precursors and/or the one or more hydrocarbon precursors to produce plasma effluents. The plasma may be formed by two electrodes within the processing chamber, which may include, for example, one or both of the showerhead 225 and the support pedestal 265 previously described. The plasma may be a bias plasma formed within the chamber region that may direct plasma effluents to the substrate surface and provide low-energy ion bombardment to the substrate to assist in the etching or removal of the tungsten-containing materials.

At operation 415, the plasma effluents may contact the substrate. The plasma effluents may include halogen-containing plasma effluents, carbon-containing plasma effluents, and/or hydrogen-containing plasma effluents. The substrate may include one or more exposed regions of the inter-layer dielectric materials and one or more exposed regions of the tungsten-containing materials. The exposed regions of the tungsten-containing materials may include tungsten oxide and/or tungsten metal in embodiments. When contacting the substrate, the plasma effluents may modify and interact with the tungsten-containing materials, while having little to no effect on the inter-layer dielectric materials. The plasma effluents may modify and interact with the tungsten-containing materials to produce volatile substances, such as tungsten oxychloride, which may then be removed from the chamber. At operation 420, at least a portion of the tungsten-containing materials may be selectively removed relative to the inter-layer dielectric materials.

The plasma formed in the processing region with the halogen-containing precursors and/or the hydrocarbon precursors may be a low-power plasma in embodiments to limit the effect on the inter-layer dielectric materials. In embodiments, the plasma power may be below or about 350 W, below or about 300 W, below or about 250 W, below or about 200 W, below or about 150 W, below or about 100 W, below or about 80 W, below or about 60 W, below or about 40 W, below or about 20 W, below or about 10 W, below or about 5 W, or lower. Utilizing a lower plasma power may improve the etch selectivity of the tungsten-containing materials to other exposed structures including the inter-layer dielectric materials. However, utilizing a higher plasma power may offer increased etch rates of the tungsten-containing materials. For example, as the plasma power increases from about 20 W to about 120 W, the etch rate of the tungsten-containing materials may be increased from at least about 100 Å per minute to at least about 700 Å per minute. As the plasma power exceeds 120 W, the increasing effect of the etch rate of the tungsten-containing material resulting from the increase in the plasma power may decrease or may be limited. Therefore, the plasma power may be maintained between about 10 W and about 250 W, between about 20 W and about 120 W, or between about 40 W and about 60 W in embodiments.

The halogen-containing precursors may include chlorine-containing precursors, bromine-containing precursors, fluorine-containing precursors, or other etchants that may interact with the tungsten-containing materials under plasma conditions. The chlorine-containing precursors may include diatomic chlorine (Cl₂), or may include chlorine-containing compounds. The chlorine-containing compounds may include chlorine forming an ionic or covalent bonding with other elements. For example, the chlorine-containing compounds may include boron trichloride (BCl₃) or tungsten chloride, such as tungsten pentachloride (WCl₅). The hydrocarbon precursors may include carbon, hydrogen, and/or nitrogen in any combination. The hydrocarbon precursors may include methyl-containing precursors in embodiments. For example, the hydrocarbon precursors may include methane (CH₄). The precursors may include additional carrier gases including chemically inert precursors including helium, argon, xenon, and other noble gases or precursors that may not chemically react with the tungsten-containing materials.

The flow rate of each of the one or more halogen-containing precursors may be less than or about 300 sccm in embodiments, and may be less than or about 250 sccm, less than or about 200 sccm, less than or about 160 sccm, less than or about 120 sccm, less than or about 80 sccm, less than or about 40 sccm, less than or about 20 sccm, less than or about 15 sccm, less than or about 10 sccm, less than or about 5 sccm, or less. The delivery of the halogen-containing precursors may be continuous during the operations of the etching method 400 in embodiments. The delivery of the halogen-containing precursors may be pulsed in embodiments. The delivery of the halogen-containing precursors may be pulsed for time periods of less than or about 60 seconds in embodiments, and may be pulsed for time periods of less than or about 55 seconds, less than or about 50 seconds, less than or about 45 seconds, less than or about 40 seconds, less than or about 35 seconds, less than or about 30 seconds, less than or about 25 seconds, less than or about 20 seconds, less than or about 15 seconds, less than or about 10 seconds, less than or about 5 seconds, or less.

The flow rate of each of the one or more hydrocarbon precursors may be less than or about 50 sccm in embodiments, and may be less than or about 45 sccm, less than or about 40 sccm, less than or about 35 sccm, less than or about 30 sccm, less than or about 25 sccm, less than or about 20 sccm, less than or about 15 sccm, less than or about 10 sccm, less than or about 5 sccm, less than or about 3 sccm, less than or about 1 sccm, or less. The delivery of the hydrocarbon precursors may be continuous during the operations of the etching method 400 in embodiments. The delivery of the hydrocarbon precursors may be pulsed in embodiments. The delivery of the hydrocarbon precursors may be pulsed for time periods of less than or about 60 seconds in embodiments, and may be pulsed for time periods of less than or about 55 seconds, less than or about 50 seconds, less than or about 45 seconds, less than or about 40 seconds, less than or about 35 seconds, less than or about 30 seconds, less than or about 25 seconds, less than or about 20 seconds, less than or about 15 seconds, less than or about 10 seconds, less than or about 5 seconds, or less.

Additionally, the flow rates of the precursors and pulsing may be combined for any of the listed numbers, depending on the desired thickness of the tungsten-containing materials to be removed. For example, the halogen-containing precursor flow rate may be between about 100 sccm and about 150 sccm and may be delivered in pulses from about 15 to about 45 seconds in embodiments. The hydrocarbon precursor flow rate may be below or about 30 sccm and may be delivered in pulses from about 15 to about 45 seconds in embodiments. Flowing the hydrocarbon precursors at lower rates relative to the halogen-containing precursors may limit or avoid carbon deposition on the substrate while achieving desired etching results. In embodiments, the hydrocarbon precursor flow rate may be less than or about 80% of the halogen-containing precursor flow rate, or may be less than or about 60%, less than or about 40%, less than or about 30%, less than or about 20%, less than or about 10%, less than or about 5%, less than or about 3%, or less than or about 1% of the halogen-containing precursor flow rate to achieve effective removal of the tungsten-containing materials.

Optional purge operations may be performed when the delivery of one or more of the precursors is paused to remove volatile tungsten-containing substances, such as tungsten oxychloride. After each purge operation, operations of method 400 may be repeated. Method 400 may represent one cycle of a process for recessing or removing tungsten-containing materials from a substrate. In some embodiments, method 400 may be repeated for at least 2 cycles, and may be repeated for at least 4 cycles, at least 6 cycles, at least 8 cycles, at least 10 cycles, at least 15 cycles, at least 20 cycles, at least 30 cycles, at least 40 cycles, at least 50 cycles, at least 60 cycles, or more. Performing method 400 in multiple cycles may improve selectivity of the tungsten-containing materials, and thereby preserve features on the substrate formed by other materials, such as inter-layer dielectric materials. The number of cycles may also depend on the amount of removal provided by each cycle. The tungsten-containing materials may be removed from a trench completely in a single cycle. In embodiments, flowing the precursors for about 30 seconds in a single cycle may remove at least about 10 nm of the tungsten-containing materials, and may remove at least about 15 nm, at least about 20 nm, at least about 25 nm, at least about 30 nm, at least about 40 nm, at least about 45 nm, at least about 50 nm, or more of the tungsten-containing materials.

As discussed above, the plasma effluents that may interact with the tungsten-containing materials may be formed from one or more halogen-containing precursors, or may be formed from a combination of the one or more halogen-containing precursors and a hydrocarbon precursor in embodiments. For example, the plasma effluents may be formed from tungsten chloride, may be formed from diatomic chlorine, may be formed from a combination of diatomic chlorine and boron trichloride, or may be formed from a combination of diatomic chlorine and methane in embodiments.

To etch the tungsten-containing materials with tungsten chloride, the temperature within the processing chamber or at the substrate level may be maintained at greater than or about 400° C. for the plasma effluents formed from tungsten chloride to interact with and etch the tungsten-containing materials on the substrate. For example, tungsten oxide may be etched at a rate of less than or about 30 Å per minute utilizing the plasma effluents formed from tungsten chloride and maintaining the temperature at about 400° C. However, such etch rate may be relatively low, which may lead to long processing times. Furthermore, as the semiconductor device feature sizes continue to reduce, an operating temperature at above or about 400° C., coupled with an etch rate of less than or about 30 Å per minute, may exceed the thermal budget of the device.

For the plasma effluents formed from one or more precursors that may include diatomic chlorine to interact with and etch the tungsten-containing materials, the temperature within the processing chamber or at the substrate level may be maintained below 400° C. in embodiments. The temperature may be maintained below or about 375° C. in embodiments, and may be maintained below or about 350° C., below or about 300° C., below or about 250° C., below or about 200° C., below or about 150° C., below or about 100° C., or lower. The temperature may also be maintained between about 100° C. and about 400° C. in embodiments, and may be maintained between about 150° C. and about 350° C., or between about 200° C. and about 300° C. during operations of the etching method 400. Volatility of processing byproducts of tungsten-containing materials, such as tungsten-oxide, may be unlikely at temperature ranges below or about 100° C., depending on other process precursors and operating conditions. Accordingly, in some embodiments the temperature during the method 400 may be maintained above or about 200° C., while being maintained below or about 400° C. to ensure operational temperatures do not exceed the processing thermal budget.

In addition to allowing for a lower temperature to achieve effective removal of the tungsten-containing materials, utilizing plasma effluents formed from the precursors including diatomic chlorine may also improve the etch rate of the tungsten-containing materials. For example, contacting the substrate with plasma effluents formed from diatomic chlorine and methane may achieve an etch rate of at least about 100 Å per minute to at least about 700 Å per minute in embodiments where the temperature within the processing chamber or at the substrate level may be maintained below 300° C. in embodiments. Contacting the substrate with plasma effluents formed from diatomic chlorine and methane may etch tungsten metal at an etch rate of at least about 100 Å per minute, at least about 150 Å per minute, at least about 200 Å per minute, at least about 250 Å per minute, at least about 300 Å per minute, at least about 350 Å per minute, or higher. Contacting the substrate with plasma effluents formed from diatomic chlorine and methane may etch tungsten oxide at an etch rate of at least about 200 Å per minute, at least about 250 Å per minute, at least about 300 Å per minute, at least about 350 Å per minute, at least about 400 Å per minute, at least about 450 Å per minute, at least about 500 Å per minute, at least about 550 Å per minute, at least about 600 Å per minute, at least about 650 Å per minute, at least about 700 Å per minute, or higher in embodiments. Tungsten oxide may be etched at a higher rate than tungsten metal in some embodiments due to the relatively weaker bonding structure, allowing plasma effluents to more easily permeate and modify the structure to form volatile substances. Given the high etch rates offered by plasma effluents formed from diatomic chlorine and methane at relatively low temperatures, the present technology may be applied to removal in fabrication of devices characterized by lower thermal budget.

Utilizing plasma effluents formed from diatomic chlorine and boron trichloride may afford etch rates of the tungsten oxide and/or tungsten metal similar to those obtained utilizing plasma effluents formed from diatomic chlorine and methane. However, plasma effluents formed from precursors including boron trichloride may also interact with and etch other materials on the substrate, such as inter-layer dielectric materials. This may be related to boron from the plasma effluents not only breaking the bonding between tungsten and oxygen but also breaking bonds between silicon and oxygen and silicon and nitrogen. Additionally, the plasma effluents formed from precursors including boron trichloride may also exhibit incomplete removal of the tungsten-containing materials.

The plasma effluents formed from diatomic chlorine and methane may limit or avoid etching the inter-layer dielectric materials. Without intending to be bound to any particular theory, carbon from the plasma effluents may break bonding between tungsten and oxygen but may have little to no effect on the bonding between silicon and oxygen and the bonding between silicon and nitrogen. For example, the method utilizing the plasma effluents formed from diatomic chlorine and methane may selectively etch the tungsten-containing materials over silicon nitride and silicon oxide, at an etch rate ratio greater than or about 100:1:1, greater than or about 200:1:1, or higher depending on the operating conditions. With enhanced etch rates and improved selectivity, the method utilizing diatomic chlorine and methane may further improve anisotropic etching of the tungsten-containing materials towards the bottom of the trench, thereby facilitating complete removal of the tungsten-containing materials from the trench while preserving the features on the substrate defined by the inter-layer dielectric materials.

Other process conditions may impact the performance of the operations as well. A pressure within the chamber may be maintained below or about 20 Torr in embodiments. The pressure may be maintained below or about 15 Torr in embodiments, and may be maintained below or about 10 Torr, below or about 5 Torr, below or about 4 Torr, below or about 3 Torr, below or about 2 Torr, below or about 1 Torr, below or about 100 mTorr, or lower. A lower pressure may provide a more anisotropic process. In embodiments the pressure may be maintained between about 500 mTorr and about 3 Torr.

Depending on the temperature and plasma characteristics used in the operations, the present technology may etch liner materials over other substrate materials. For example, the liner may include one or more metals, including transition metals, as well as nitrides of metals. The metals may include, for example, titanium, titanium nitride, tantalum, tantalum nitride, ruthenium, and other materials and nitrides. The present technology may selectively etch the liner materials, such as titanium nitride, over the inter-layer dielectric materials, such as silicon nitride and/or silicon oxide, at an etch rate ratio greater than or about 50:1, and in embodiments greater than or about 100:1, greater than or about 150:1, greater than or about 200:1, or more in embodiments.

Turning to FIGS. 5A-5C are shown cross-sectional views of substrates on which the present technology may be performed. FIG. 5A illustrates a cross-sectional view of a portion of a substrate 505 on which a trench or via has been formed. The trench may be formed within or through one or more layers formed on the substrate 505. In this embodiment, the trench is formed through a layer of a first inter-layer dielectric material 506, such as silicon oxide, and extends into a layer of a second inter-layer dielectric material 507, such as silicon nitride. In other embodiments, the trench may be formed through or within only one layer or more than two layers of the same or different materials on the substrate 505. The one or more layers of materials may be dielectric materials, metallic materials, or any suitable materials to achieve a desired structure. A liner 510 may be formed within the trench and may produce a barrier on the sidewalls and the substrate. The liner may include titanium nitride, tantalum nitride, other transition metals or transition metal nitrides, and may protect the substrate 505 from metal diffusion. In some embodiments, the substrate may not include a liner or may include more than one liner. One or more tungsten-containing materials may be formed or deposited within the trench and on the liner material 510. In this embodiment, tungsten metal 515 and tungsten oxide 516 are disposed inside the trench with the tungsten metal 515 positioned at the bottom of the trench. In some embodiments, tungsten oxide may be disposed at the bottom of the trench. In some embodiments, only tungsten metal or only tungsten oxide may be disposed inside the trench, or more than one layer of tungsten metal and/or more than one layer of tungsten oxide may be disposed inside the trench.

FIG. 5B illustrates a plasma etching of one or more tungsten-containing materials in which plasma effluents 520 of one or more halogen-containing precursors and/or one or more hydrocarbon precursors are produced. The precursors may be flowed into a substrate processing region where a plasma may be formed to produce the plasma effluents 520. The tungsten oxide 516 and the liner 510 may be contacted with the plasma effluents 520 to produce volatile substances, which may be extracted from the chamber. After the tungsten oxide 516 has been removed, the tungsten metal 515, along with the surrounding liner 510, may be exposed and may be contacted with the plasma effluents 520 to produce volatile substances, which may be extracted from the chamber. The volatile substances produced by the effluents 520 contacting the tungsten-containing materials 515, 516 may include tungsten oxychloride and/or tungsten chloride. As illustrated in FIG. 5C, the plasma effluents may contact and completely remove the tungsten oxide 516, the tungsten metal 515, and the liner 510 from the trench whiling having little or no effect on the first and second inter-layer dielectric materials 506, 507. By utilizing removal methods according to embodiments of the present technology, improved removal of tungsten-containing materials may be performed under restricted thermal budgets, and improved selectivity over other exposed materials, including silicon oxide or silicon nitride, may be achieved.

In the preceding description, for the purposes of explanation, numerous details have been set forth in order to provide an understanding of various embodiments of the present technology. It will be apparent to one skilled in the art, however, that certain embodiments may be practiced without some of these details, or with additional details.

Having disclosed several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the embodiments. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present technology. Accordingly, the above description should not be taken as limiting the scope of the technology. Additionally, methods or processes may be described as sequential or in steps, but it is to be understood that the operations may be performed concurrently, or in different orders than listed.

Where a range of values is provided, it is understood that each intervening value, to the smallest fraction of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Any narrower range between any stated values or unstated intervening values in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of those smaller ranges may independently be included or excluded in the range, and each range where either, neither, or both limits are included in the smaller ranges is also encompassed within the technology, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.

As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, reference to “a precursor” includes a plurality of such precursors, and reference to “the layer” includes reference to one or more layers and equivalents thereof known to those skilled in the art, and so forth.

Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”, “include(s)”, and “including”, when used in this specification and in the following claims, are intended to specify the presence of stated features, integers, components, or operations, but they do not preclude the presence or addition of one or more other features, integers, components, operations, acts, or groups. 

The invention claimed is:
 1. An etching method comprising: flowing a chlorine-containing precursor into a processing region of a semiconductor processing chamber; flowing methane into the processing region of the semiconductor processing chamber; forming a plasma from the chlorine-containing precursor and the methane to produce plasma effluents; contacting a substrate with the plasma effluents, wherein the substrate comprises an exposed region of a tungsten-containing material, and wherein the plasma effluents produce an oxychloride of tungsten; and recessing the exposed region of the tungsten-containing material.
 2. The etching method of claim 1, wherein the tungsten-containing material comprises at least one of tungsten oxide or tungsten metal.
 3. The etching method of claim 1, wherein the etching method removes the tungsten-containing material at a rate of at least about 200 Å per minute.
 4. The etching method of claim 3, wherein the etching method removes the tungsten-containing material at a rate of at least about 400 Å per minute.
 5. The etching method of claim 1, wherein the substrate further comprises an exposed region of a silicon-containing material, and wherein the etching method has a selectivity of the tungsten-containing material to the silicon-containing material greater than or about 100:1.
 6. The etching method of claim 5, wherein the silicon-containing material defines a trench within which at least a portion of the tungsten-containing material is disposed, the trench having an aspect ratio of about 10:1 or greater, and wherein the etching method completely removes at least the portion of the tungsten-containing material disposed within the trench.
 7. The etching method of claim 1, wherein a temperature of the substrate is maintained between about 200° C. and about 400° C. during the etching method.
 8. The etching method of claim 7, wherein the temperature of the substrate is maintained at about 250° C. during the etching method.
 9. The etching method of claim 1, wherein a plasma power of the plasma formed from the chlorine-containing precursor and the methane is at least about 5 W.
 10. The etching method of claim 1, wherein a plasma power of the plasma formed from the chlorine-containing precursor and the methane is less than or about 250 W.
 11. The etching method of claim 1, wherein a pressure within the semiconductor processing chamber is maintained below or about 3 Torr.
 12. The etching method of claim 1, wherein the etching method is repeated for at least two cycles.
 13. The etching method of claim 12, wherein each of the at least two cycles lasts less than or about 30 seconds.
 14. The etching method of claim 1, wherein a flow rate of the methane is below or about 30 sccm.
 15. The etching method of claim 1, wherein the chlorine-containing precursor comprises diatomic chlorine.
 16. The etching method of claim 15, wherein a flow rate of the diatomic chlorine is about 120 sccm.
 17. An etching method comprising: flowing a chlorine-containing precursor into a processing region of a semiconductor processing chamber; flowing a hydrocarbon precursor into the processing region of the semiconductor processing chamber; forming a plasma from the chlorine-containing precursor and the hydrocarbon precursor to produce plasma effluents; contacting a substrate with the plasma effluents, wherein the substrate comprises a first region of a tungsten-containing material and a second region of a first silicon-containing material, and wherein the substrate further comprises a metal nitride liner interposed between a third region of the tungsten-containing material and a fourth region of a second silicon-containing material; selectively etching the first region of the tungsten-containing material relative to the second region of the first silicon-containing material; and selectively etching the metal nitride liner relative to the first and the second silicon-containing material.
 18. The etching method of claim 17, wherein the plasma effluents produce an oxychloride of tungsten.
 19. An etching method comprising: flowing diatomic chlorine at less than or about 250 sccm into a processing region of a semiconductor processing chamber; flowing methane at less than or about 50 sccm into the processing region of the semiconductor processing chamber; forming a plasma from the diatomic chlorine and the methane at a plasma power of between about 10 W and about 250 W to produce plasma effluents; contacting a substrate with the plasma effluents, wherein the substrate comprises an exposed region of a tungsten-containing material and an exposed region of a silicon-containing material; etching the exposed region of the tungsten-containing material at a rate of at least about 400 Å per minute, wherein the etching method has a selectivity of the tungsten-containing material to the silicon-containing material greater than 100:1; wherein a temperature of the substrate is maintained at about 250° C. during the etching of the exposed region of the tungsten-containing material; and wherein a pressure of the semiconductor processing chamber is maintained at or below about 10 Torr during the etching of the exposed region of the tungsten-containing material. 